function rgb=hsi2rgb(hsi)
%HSI2RGB Converts an HSI image to RGB.
%   HSI2RGB Converts an HSI image to RGB, where HSI is assumed to be of
%   class double with:
%       hsi(:,:,1)= hue image normalized values to the range [0,1] by
%                   dividing all angle values by 2*pi.
%       hsi(:,:,2)=saturation image, in the range [0,1].
%       hsi(:,:,3)=intensity image, in the range [0,1].
%   The components of the output image are:
%       rgb(:,:,1)=red;
%       rgb(:,:,2)=green.
%       rgb(:,:,3)=blue.
%Extract the individaul HSI component images.
H=hsi(:,:,1)*2*pi;
S=hsi(:,:,2);
I=hsi(:,:,3);

%Implement the conversion equations.
R=zeros(size(hsi,1),size(hsi,2));
G=zeros(size(hsi,1),size(hsi,2));
B=zeros(size(hsi,1),size(hsi,2));

% RG sector (0<=H<2*pi/3).
idx=find((0<=H)&(H<2*pi/3));
B(idx)=I(idx).*(1-S(idx));
R(idx)=I(idx).*(1+S(idx).*cos(H(idx))./cos(pi/3-H(idx)));
G(idx)=3*I(idx)-(R(idx)+B(idx));
%BG sector (2*pi/3<=H<4*pi/3).
idx=find((2*pi/3<=H)&(H<4*pi/3));
R(idx)=I(idx).*(1-S(idx));
G(idx)=I(idx).*(1+S(idx).*cos(H(idx)-2*pi/3)./cos(pi-H(idx)));
B(idx)=3*I(idx)-(R(idx)+G(idx));
%BR sector.
idx=find((4*pi/3<=H)&(H<=2*pi));
G(idx)=I(idx).*(1-S(idx));
B(idx)=I(idx).*(1+S(idx).*cos(H(idx)-4*pi/3)./cos(5*pi/3-H(idx)));
R(idx)=3*I(idx)-(G(idx)+B(idx));
%Combine all three results into an RGB image. Clip to [0,1] to compensate for floating-point arithmetic rounding effects.
rgb=cat(3,R,G,B);
rgb=max(min(rgb,1),0);

